<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="demo5.css">
    </head>

    <body>
        <h1>这是标题1</h1>
        <h2>这是标题2</h2>
        <p id="no1">这是段落</p>
        <p class="no2">这个段落设置了内边距</p>
        <br />
        <p class="flower">我是一个有背景的段落。</p>
        <p class="no3">Hello World</p>
    </body>
</html>